Update 29/05/2008: There may still be chance (again) for the game to appear on systems other than those confirmed.
According to Kombo, the game has been tagged with "To be determined" after the initially announced systems - giving some hope for those wanting a Nintendo release:
"Format: Xbox 360, PlayStation 3 system, PC, To be determined," and "Release date: TBA (Xb360, PS3, PC, TBD)."
Original Story 28/05/2008:
Capcom have confirmed Street Fighter IV will not be heading to the Wii.
Recent rumours suggested that the game would not be making its way to Nintendo's Wii, despite Capcom's enthusiasm to spread the Street Fighter love. Today Capcom has confirmed that Street Fighter IV will be be heading to Xbox 360, PlayStation 3 and PC, with no mention of a Nintendo Wii or DS release.
A different version of the game or unique entry in the series may still be on the cards as Capcom has yet to comment on the lack of a Nintendo version of the next-generation Street Fighter.